Transapical mitral valved stent implantation: computed tomographic evaluation of different prototype designs.

AIMS: The evaluation of in vivo shaping of mitral valved stent prototypes using cardiac computed tomography (CT) was the focus of this study. METHODS AND RESULTS: Twelve pigs received a self-expanding mitral valved stent, composed of an atrial element connected to a tubular ventricular body at a modified angle (45°, 90°, 110°) resulting in three designs. Cardiac CT was performed three weeks after implantation, with focus placed on stent design-related parameters: possible left ventricular outflow tract obstruction and stent shaping. CT was successfully conducted in 11/12 animals showing correct stent position within the mitral annulus and no obstruction of the left ventricular outflow tract in 9/11 animals. Minor radial deformations of the stent body were detected. At the atrioventricular junction, deformations of the stent structure were observed in all cases. Stents with a 45° angle exhibited the greatest deflection (≤56.4°±14.5°). CONCLUSIONS: The effectiveness of cardiac computed tomography in the development process of valved stents to provide essential information and quantitative data about the in vivo stent geometry was demonstrated. The in vivo mechanical deformations of the stent were quantified, identifying critical design areas: a larger preset angle leads to less deflection and improved alignment and hence reduces the mechanical load.

Comparison of different resection tools for human calcified aortic valves.

OBJECTIVE: Symptomatic severe aortic valve stenosis is a disease primarily found in patients of advanced age. The standard therapy is the aortic valve replacement. Transcatheter aortic valve implantation (TAVI) is a treatment for patients ineligible for conventional aortic valve replacement. To minimize the incidence of TAVI-related complications, such as paravalvular leakage, pacemaker necessity, and ostial coronary occlusion, our research group works on the development of resection tools for aortic valves. The aim of this study was to investigate ex vivo different resection tools for human calcified aortic valves concerning cross-section morphology. METHODS: With the use of 12 human calcified aortic leaflets, the effect of laser scalpel, punching device, and scissors on cross-section morphology was investigated. Scanning electron microscopy and histological analyses were applied to evaluate the cutting surface area. RESULTS: The cross-section areas created by a laser scalpel were smooth, regular, and uniform, whereas these areas were rough, irregular, and inhomogeneous when using the scissors or the punching device. Quantitative analysis of the cutting edges demonstrated significant differences between the three resection tools. The best results were obtained for the laser scalpel compared with the punching device (P < 0.001) and for the laser scalpel compared with the scissors (P < 0.05), whereas the scissors compared with the punching device showed no significant differences (P > 0.05). CONCLUSIONS: Laser cutting of human calcified aortic valves demonstrated the best results concerning homogeneous cross-section morphology compared with the punching device and the scissors and seems to be a promising tool for aortic valve resection during TAVI procedures in the future.

Off-pump tricuspid valved stent implantation: the next step.

OBJECTIVES: Off-pump transcatheter valved stent implantation could be a treatment option for patients suffering from symptomatic tricuspid regurgitation (TR) who are classified as inoperable. In this study, we present our recent short-term results of transventricular tricuspid valved stent implantation and compare different stent types for atrial anchorage. METHODS: Fifteen pigs received a self-expandable valved stent implantation off-pump via a transventricular access. Successfully implanted pigs were observed over a period of 6 h (n = 9), 48 h (n = 1) and 4 weeks (n = 1). Haemodynamic and full transoesophageal echocardiographic (TOE) evaluations were done before, 1 h, 3 h (n = 11; all successfully implanted pigs), and 6 h (n = 9; acute group) after implantation. Nine days postimplantation, one pig received additional angiography, computed tomography (CT) and transthoracic echocardiography (TTE). Post-mortem, gross examination was conducted to analyse the stent position and deformation. In two pigs (48 h and 4 weeks survival) histological staining and immunohistochemistry of surrounding myocardium was performed. RESULTS: The heart rate significantly increased in all pigs postimplantation from 66.8 ± 13.6 to 101.8 ± 24.6 bpm, whereas cardiac output and pressure levels remained unchanged. Orthotopic positioning was reproducibly achieved. TOE showed an efficient reduction of paravalvular leakages from a mean grade of 1.4 1 h postimplantation to a mean of 0.9 at 6 h postimplantation due to a special sealing pouch. The ratio early and late ventricular filling velocities remained constant and the valvular gradient across the valved stent stayed low during the observation period. Angiography, CT and TTE confirmed orthotopic positioning and mild grade of paravalvular leakage after 9 days (n = 1). Only mild TR was observed here. The ventricular part of the stent was deformed to an oval shape in 7 of 14 animals as shown via post-mortem examination. The surrounding tissue after 1 month (n = 1) showed normal morphology, without inflammation or calcification. CONCLUSION: This study shows the feasibility of catheter-based replacement of the tricuspid valve by a valved stent in an off-pump procedure. The successive enhancements in this tricuspid valved stent design lead to a prototype being ready for mid- to long-term evaluations.

Transapical mitral valved stent implantation: comparison between circular and D-shaped design.

AIMS: In this study two designs of a self-expanding valved stent were compared after off-pump implantation into the mitral valve to identify the superior one. METHODS AND RESULTS: Two designs of a mitral valved stent were tested. The first design is composed of a circular atrial element connected to a tube-shaped ventricular element. In the second design, the atrial element is D-shaped to achieve better anatomical alignment. Prior to in vivo testing, the area with the highest risk of PVL was identified in a hydrostatic in vitro set-up. Subsequently, eight pigs received stents (circular, n=5; D-shaped, n=3) via apical access in the beating heart. Positioning and haemodynamics were evaluated by TEE and invasive pressure measurement pre-implantation, after 1 hr, and at two and four weeks. In vitro testing showed less PVL in the anteromedial region in D-shaped design stents (p<0.001). All stents were successfully deployed in vivo and six animals maintained normal haemodynamics for two weeks or longer. Rotational reorientation of all stents with D-shaped elements was observed. Both groups indicated no clinically relevant gradients over the mitral valved stent. CONCLUSIONS: This study demonstrates that the circular design was superior to the D-shaped model after rotational reorientation of the latter occurred.

Tricuspid valved stent implantation: novel stent with a self-expandable super-absorbent polymer.

OBJECTIVE: Trans-catheter aortic and pulmonary valve replacement procedures can result in favorable outcomes in selected patients. The aim of this study was to investigate the functioning of a novel self-expanding valved stent with super-absorbent polymer (SAP) for minimally invasive replacement of the tricuspid valve. METHODS: A newly designed nitinol stent with SAP was specially designed for the tricuspid annulus. This device was composed of right atrial anchoring elements, a left ventricular tubular stent, and a trileaflet bovine pericardial valve. The stent was coated with a waterproof material, and a pouch containing SAP for minimizing paravalvular leakage was placed beneath the atrial element. Seven pigs underwent minimally invasive off-pump tricuspid valved stent implantation. This was performed through a lower ministernotomy using a transventricular approach under transesophageal echocardiographic guidance. After 1 and 6h, a complete echocardiographic evaluation and hemodynamics (Swan-Ganz catheter) were performed. RESULTS: Six of seven pigs exhibited normal hemodynamics immediately after tricuspid valved stent implantation and maintained stability for the entire period of monitoring. In one pig, a part of the atrial stent elements was deployed into the right ventricle, leading to significant paravalvular leakage, and died very soon. All subsequent animals survived with good results in the observation period. Accurate positioning of the valved stent was documented in six of seven pigs. SAP expanded and filled the gap between the stent and the native annulus in all animals. Mild paravalvular leakage was found in two of the six animals. Nevertheless, the observed leakage decreased to trace levels 6h after implantation. In the additional four pigs, only trace tricuspid regurgitation was revealed. No right ventricular outflow tract obstruction was detected. CONCLUSIONS: Trans-apical off-pump tricuspid valved stent implantation is feasible in an acute experimental setting, and SAP may help to reduce paravalvular leakages.